Heat
Heat is transferred to and from objects through three processes. Say them.
Conduction, convection and radiation.
Define freezing
Freezing is the change of state at which a liquid becomes solid.
What's the difference between an heterogeneous mixture and homogeneous mixture?
We can distinguish components of an hetergeneous mixture whereas we can't do it with an homogeneous mixture.
What is a solution? Give an example.
A solution is a homogenenous mixture.
E.g. salt water
Say the separation techniques corresponding to hterogeneous mixtures.
Sieving, filtration, magnetic separation, decantation and centrifugation.
Complete the sentence:
Heat is transferred from a _____ (cooler/warmer) object to a _____ (cooler/warmer) object.
Heat is transferred from a warmer object to a cooler object.
Define freezing point
Freezing point is the temperature at which a liquid becomes solid.
What's the difference between an element and a compound?
Both are pure substances. Elements are composed of the same type of atoms whereas compounds are composed of different types of atoms.
Which are the parts of a solution?
Solute and solvent.
Say the materials that you need to do:
1) Magnetic Separation
2) Sieving
3) Centridugation
1) Magnet
2) Sieve
3) Centrifuge and test tubes
Is it true of false?
Particles are necessary to transfer heat through radiation.
Give an example about heat transfer through radiation.
False. Particales are not necessary to transfer heat through radiation.
E.g. We feel the warmth of the Sun by radiation.
E.g. Our bodies radiate heat.
Is it true or false? If it's false, correct the sentence.
During melting, temperature is increasing.
False. During a change of state, the temperature is always fixed.
During melting, temperature doesn't change, in fact, this temperature is called the melting point.
What's the difference between a pure substance and a mixture?
In a pure substance, atoms are in a fixed proportion and properties of the substance are the same in every part of it.
In a mixture, the proportion of the components is not fixed and the properties of the mixture might change in each part of the mixture.
Which is the component in the bigger proportion?
Solvent.
When do we use magnetic separation?
We use mangetic separation when one of the components of the mixture is ferromagnetic and the rest of them aren't.
Correct the sentence:
Conduction is the main process to transfer heat in gases. It's not necessary that "objects/substances" are in direct contact with each other.
Give an example of about transferring heat through conduction.
Conduction is the main process to transfer heat in solids. It's not necessary that "objects/substances" are in direct contact with each other.
E.g. When you touch a mug of hot chocolate, heat goes from the mug to your hands through conduction.
Say a similarity and difference between the boiling point and condensation point.
Similarity: Both the condensation point and boiling point correspond to the same number.
Difference: The condensation point is the temperature at which a gas becomes liquid. Boiling point is the temperature at which a liquid becomes gas.
Say a synonym of homogeneous mixture. Give an example of that type of mixture.
A homogeneous mixture is also called a solution.
Name the types of solution. What's the difference among them?
Diluted, concentrated, saturated, supersaturated.
The difference among them is the concentration. The diluted one has a smaller concentration than the supersaturated.
When do we use filtration?
To do filtration, the mixture has to be composed of a liquid and a solid, and the solid is not soluble into the liquid.
Explain how a hot air balloon flies (including heat transfer processes).
When the air inside the balloon is heated, the air becomes less dense. The surrounding colder air falls beneath the hot air. This forces the warm air with it. The moving warm air creates a convection current.
What are the differences between evaporation and boiling?
Both are related to a change of state of a substance from liquid to gas.
Evaporation only affects the surface of the substance and occurs at any temperature.
Boiling point affects the entire substance and occurs at a specific temperature (boiling point).
Are all homogenous mixtures in a liquid state?
If your answer is not, give examples of this type of mixture in each state.
No, they are not.
Gaseous state: air
Liquid state: sea water
Solid state: steel, brass
Rephrase these sentences:
1) The concentration of salt in soup is 5 g/L.
2) The concentration of sugar in the cake is 25%.
1) There is 5g of salt per each litre of soup.
2) There is 25g of sugar per 100g of cake.
Say the materials to do a distillation.
(You can draw them on a piece of paper and show it to the rest of the class.)
Stand, bunsen burner, distillation flask, thermometer, condenser, and beaker/Erlenmeyer flask.