Thermal and Electrical Conductors and Insulators
Name one common thermal conductor used in cooking.
Metal
What state of matter has a definite shape and volume?
Solid
Is sugar soluble or insoluble in water?
Soluble
What happens to water when it freezes?
It turns to ice/It turns to a solid
What state of matter takes the shape of its container but has a fixed volume?
Liquid
Which of the materials are used in electrical wires?
A. iron
B. copper
C. steel
D. aluminum
Copper
What process turns a liquid into a gas?
Is sand soluble or insoluble in water?
Insoluble
What gas is produced when baking soda reacts with vinegar?
Carbon dioxide
Name a material that is a good thermal insulator.
Wool, plastic, rubber
Why is plastic often used to cover electrical wires?
Because plastic is an electrical insulator
How do gases move in a room when you open a perfume bottle?
The gas spreads out (diffuses) and moves around the room.
What method can be used to recover salt from saltwater?
Evaporation
Name what is needed for something to burn and rust.
Burn (heat, fuel, oxygen)
Rust (oxygen, water, iron or steel)
Name one use of a filter in everyday life.
Coffee filter, air fliter, water filter, vacuum filter
Why does a wooden spoon stay cool longer than a metal spoon when placed in hot soup?
Wood is a poor thermal conductor (insulator)
Sharul and Mohammad had a hot cup of tea placed on a table. They realised that something was being released from the tea. Explain what and how does this happen?
The tea is hot. Gas such as water vapour is being released from the tea. Evaporation is taking place.
You are given a mixture of sugar, sand, and water. Explain how you can separate the sugar and sand from the water, and how you can tell which one is soluble and which one is insoluble.
First, dissolve the mixture in water. Sugar will dissolve because it is soluble, while sand will not dissolve because it is insoluble. Then, filter the mixture to separate the sand from the sugar solution. Finally, evaporate the water to recover the sugar.
You melt a block of chocolate, and then let it cool down to become solid again. Explain why this is considered a reversible change, and what conditions are needed for the chocolate to return to its original form.
This is a reversible change because the chocolate can go from solid to liquid when heated and then back to solid when cooled. No new substances are formed, and the change can be undone by changing the temperature.
When you mix baking soda and vinegar, you see fizzing and bubbles form. This is an example of an irreversible change. Can you explain why the reaction can't be reversed and what new substance is created during the fizzing?
The reaction between baking soda and vinegar produces carbon dioxide gas, which causes the fizzing and bubbles. This is an irreversible change because you can't turn the gas or the other new substances (like water and a type of salt) back into the original baking soda and vinegar.
You are helping to design a new set of headphones. The wires inside the headphones need to carry electricity to the speakers, but the parts you touch should stay safe. You can use copper, rubber, or plastic for different parts. Which material would you use for the wires, and which for the outer covering? Explain your choices based on the properties of conductors and insulators.
I would use copper for the wires because copper is a good electrical conductor, which allows electricity to flow easily to the speakers. For the outer covering, I would use rubber or plastic because both are electrical insulators, which prevent electricity from passing through, making the headphones safe to touch.
Imagine you have ice (a solid), water (a liquid), and steam (a gas). All three are made of the same substance—water. Explain what occurs at each stage the substance is at and how it can change from one state to another.
Ice forms at low temperatures (solid), water at normal temperatures (liquid), and steam at high temperatures (gas).
You are working in a science lab and accidentally spill a mixture of salt, sand, and water onto a tray. You need to clean up the mess quickly, and you want to recover the salt and the sand. You have access to basic tools like a filter, a heating source, and a container. What steps would you take to separate the sand and salt from the water, and why would you choose each method?
First, I would use a filter to separate the sand from the saltwater because sand is insoluble and will remain in the filter. Then, I would use evaporation by heating the saltwater to remove the water and recover the salt, as salt is soluble in water and will be left behind once the water evaporates.
When you burn wood, it turns into ash. Why do you think burning is an irreversible change, and how is it different from melting ice?
Burning changes wood into new substances (ash, gas), while melting ice is reversible because ice can refreeze back into water. Melting does not create new substances.
You are asked to design a handle for a cooking pot. The pot gets very hot, and you need to choose a material for the handle that will keep it cool to the touch. You have two options: metal and wood. Which material would you choose for the handle, and why?
I would choose wood for the handle because wood is a good thermal insulator, meaning it does not conduct heat well. This would prevent the heat from the pot from traveling to the handle, keeping it cool. Metal, on the other hand, is a good thermal conductor and would get hot quickly.