Physical or Chemical?
Is melting ice cream a physical or a chemical change?
Physical change
Name the three most common states of matter.
Solid, liquid, gas
Liquid → solid. What is this change called?
Freezing
During cooling, heat moves from a ______ object to a ______ object.
From a hotter object to a colder one
You need a flame to heat something in the lab. Which equipment do you use?
A burner
Is the rusting of iron a physical or a chemical change?
Chemical change (a new substance forms)
Which state has a definite shape AND a definite volume?
Solid
Solid → liquid. What is this change called?
Melting
When a substance is heated, how do its particles move?
Faster, because they gain kinetic energy
Ouch! The test tube is very hot. What do you use to hold it so you don’t burn your fingers?
Test tube holder
Sugar dissolves in water. Physical or chemical? Why?
Physical. No new substance is formed.
Which state has a definite volume but takes the shape of its container?
Liquid
You hang wet clothes outside on a sunny day. After a few hours they are dry. Where did the water go? What is this change called?
The water turned into water vapor and went into the air. This is evaporation (liquid → gas).
You forget a bottle of water in the freezer. The next day it is solid ice. At what temperature did the water start to freeze, and what did the freezer take away from the water?
At 0 °C. The freezer took heat away from the water
You want to pour a liquid into a bottle with a very narrow neck without spilling it. What do you use?
Funnel
Name TWO signs that a chemical change has happened.
Any two: gas bubbles, color change, temperature change, a new solid forms, light, new smell
When you open a perfume bottle, people across the room can smell it. Why does the gas spread everywhere?
Gas particles are far apart and move freely, so a gas spreads out to fill the whole space.
You take a cold bottle of juice out of the fridge. Soon tiny water drops appear on the outside of the bottle. Where did the water come from?
From water vapor in the air. It touches the cold bottle, cools down and turns into liquid. This is condensation (gas → liquid).
In winter, why do your cold hands feel warmer when you hold a cup of hot tea?
Heat moves from the hotter object (the tea cup) to the colder object (your hands).
You need EXACTLY 25 mL of water. Should you use a beaker or a graduated cylinder? Why?
A graduated cylinder. It measures exact volumes, but a beaker only measures approximate volumes.
A candle burns. Name one physical change and one chemical change.
Physical: wax melts or evaporates. Chemical: wax vapor reacts with oxygen to make carbon dioxide and water.
Your body has all three states of matter! Name one solid, one liquid, and one gas in the human body.
Solid: bones or teeth. Liquid: blood or saliva. Gas: air in the lungs (oxygen or carbon dioxide).
On a cold winter morning, snow on the ground slowly disappears, but no puddles of water appear. What happened to the snow?
The snow turned directly from solid ice into water vapor without melting first. This is sublimation (solid → gas).
Water in a teapot is already boiling at 100 °C. Mom turns the fire up higher. Will the water get hotter than 100 °C? Explain.
No. While water is boiling, its temperature stays at 100 °C. The extra heat is used to turn the water into steam (gas).
This flask has a cone shape and a narrow neck. We use it for mixing and keeping toxic substances. What is its name, and how does its shape help?
Erlenmeyer (conical) flask. The narrow neck stops liquids from splashing out when you mix them.