Elements, Compounds, & Mixtures
What is the smallest unit of an element?
Atom
What type of change is melting ice?
Physical change
Name the three types of matter
Gas, liquid, solid
What does “dissolve” mean?
One substance mixes evenly into another
What is the formula for speed?
Speed = Distance ÷ Time
What do you call a pure substance made of two or more elements chemically combined?
Compound
What type of change forms a new substance?
Chemical change
What are 2 physical properties
Color, shape, mass, volume, texture, density, etc
What can increase the rate of dissolving?
Stirring, heating, or crushing
What is the difference between speed and velocity?
Velocity includes direction; speed does not
What type of mixture looks the same throughout?
Homogeneous mixture
What are 2 signs of a chemical change?
Color change, gas/bubbles, odor, temperature change, or new solid forms
What property determines if an object sinks or floats?
Density compared to water
How does surface area affect dissolving rate?
More surface area = faster dissolving
If a car travels 100 m in 20 seconds, what’s its speed?
5 m/s
How are elements and compounds different?
Elements have one type of atom; compounds have two or more chemically combined
Is cutting paper a chemical or physical change? Explain.
Physical; no new substance is formed
Which is a physical property — color or burning?
Color
Why does sugar dissolve faster in hot water than cold?
Higher temperature gives particles more energy to move
On a distance-time graph, what does a flat (horizontal) line mean?
The object stopped moving
Give one example of a mixture and one example of a compound
Mixture: salad; Compound: water (H₂O)
Burning wood shows a chemical change. What evidence proves this?
New gases and ash form; temperature and color change
What is one way you can change the shape of matter without changing what it is?
Answer: Cut, crush, or bend it (physical change
Is dissolving a physical or chemical change? Explain.
Physical; the substance keeps its identity
A runner moves 50 m north in 10 seconds. What’s the velocity?
5 m/s north